In my opinion, there are two main problems with both of those splits in general:
- not enough legs
- too much shoulders
Doing legs just once a week is, quite probably, not enough. Yes, you can kill yourself in that one weekly session, but it always seemed to me that too much time has passed since the last time I squatted and it felt like training and than undertraining before I train again One possibility is to do deads on your back day, so that you get some medium quad work on that day.
Another issue is that practically all compound upper body movements involve shoudlers. Some even to great degree, even though they are not considered shoulder movements, like Rows. And, in split #2, your shoudlers essentially get hit 3x a week. Now, you may adapt to that and make progress, but I think it’s much more likely shoudlers will become a bottleneck of your upper body progress.
If you want to try higher volume, I think upper/lower split would work better. In fact, I don’t see anything wrong with ABBH - it has plenty of volume: 10x3-5 and 5x10 in the same week for all basic planes of movement. What more could a man want :)))
But, if you insist on using a 3-way split, then a good option can be to focus on main lifts: Squat - Bench - Deadlift, and fill the rest of the day with assistance for those lifts. Like this:
Back Squat, Step-ups, Hypers or GHR, Abs
Bench Press, Barbell Row, DB Incline, Triceps
Deadlift, Push Presses snd/or Power Cleans, Pullups, Curls